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  • Electronic Resource  (36)
  • 2005-2009
  • 1985-1989  (29)
  • 1975-1979  (7)
  • 1925-1929
  • 1987  (18)
  • 1986  (11)
  • 1976  (7)
Material
  • Electronic Resource  (36)
Years
  • 2005-2009
  • 1985-1989  (29)
  • 1975-1979  (7)
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1047-1054 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive photo-Hall investigation of compensation densities in n-type Hg1−xCdxTe (0.224〈x〈0.235) is reported. The technique consists of measuring the low-temperature electron mobility as a function of optically excited carrier density. Pulses of 25-μs duration from a CO2 laser yield excess electron-hole plasma densities of between 1013 and 1016 cm−3. At low excitation levels the mobility increases due to the neutralization of ionized acceptors by photoexcited holes, while at higher excitation levels the mobility slowly decreases due to electron-hole scattering. By comparing to a detailed theory for electron transport in photoexcited narrow-gap semiconductors, the density of compensating acceptors NA can be accurately determined. The theory is generalized to account for multi-ion scattering, carrier heating, surface conduction, and inhomogeneous excitation. Experimental refinements significantly extending the range of narrow-gap n-type samples for which compensation densities may be determined are discussed. The present study demonstrates the broad applicability of the technique by determining NA for samples with compensation ratios between 0.09 and 0.96 and with both single and double acceptors.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 843-851 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel, active, mode-locking scheme for producing single, line-tunable, high-power ultrashort CO2-laser pulses is described. Using an auxiliary grating-tuned cw CO2 laser for injection locking on the 9R(16) line, the Q-switched, mode-locked, and cavity-dumped 10-atm CO2 laser produces single, detection-limited (〈500 ps) pulses of 5-mJ energy at λ=9.29 μm. Details are given on the traveling-wave GaAs Pockels cells, both of which are controlled by a single, ultraviolet (UV) triggered spark gap. The time-locked output pulse is delayed by precisely 300.7 ns with 〈±50 ps jitter against the UV triggered spark gap, so the laser pulse is synchronizable to an external event to 〈±250 ps. To drive the transverse-electric (TE) 10-atm amplifier section, instead of the conventional Marx bank or inductance-capacitance (LC) generator, a new type of circuit is used. The automatically preionized, double-sided LC inversion circuit uses only one spark gap, and a detailed description with operating characteristics is provided.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 261-264 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel TE discharge, 15-mm aperture, multiatmosphere, CO2 laser amplifier is described, with measured electrical characteristics and gain measurements on the 9.294-μm, 9R(16) line. The electrical circuit used in this amplifier is a realistic alternative to the Marx bank or conventional LC inversion circuit and, similarly, it would be useful for excitation of other gas lasers as well. This automatically preionized, double-sided, fourfold LC inversion circuit uses only one spark gap, and it is shown to provide small-signal gains of 5.7% cm−1, at 120 J l−1 atm−1 and 10 atm. The generalization to an n–stage device, which would be suitable for higher pressures, and larger apertures, is discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 2313-2322 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temporal growth rates, spatial behavior, and saturation characteristics of stimulated Brillouin scattering (SBS) occurring in a CO2 laser–gas jet experiment are investigated experimentally by picosecond Thomson scattering of ruby laser light as well as by intensity and spectral measurements of the backscattered light. Exponential temporal growth of the ion acoustic waves was observed and found to have a growth rate in good agreement with theory. Spatial modulations in the ion-acoustic-wave amplitude resulting from plasma inhomogeneities were found to limit the backscattered reflectivity to less than 10%. The ion acoustic waves saturate at a fluctuation amplitude of 〈20%. Ion trapping is shown to account for the observed saturation as well as temporal modulations in the ion-acoustic-wave amplitude and sibebands in the backscattered spectra.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 17 (1987), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Single-station diel oxygen curves were used to monitor the oxygen metabolism of the Ogeechee River, a sixth-order blackwater river in the Coastal Plain of southeastern U.S.A., over a period of 4 years. Ecosystem production (P) and respiration (R) were estimated, and P/R ratios calculated to determine the extent of autotrophy characteristic of this type of river. The potential error in oxygen metabolism caused by photo-oxidation of dissolved organic carbon (DOC) in the water was measured and found to be minor.2. Rates of ecosystem primary production measured were intermediate compared to other rivers, ranging from 0.49 to 13.99g O2m−2 day −1.Primary production rates were highest during the summer when water levels were low. Regression analysis indicated that water depth and light absorption by DOM were significant predictors of primary production in this river. Incident light intensities were not significantly correlated with production rate.3. Respiration rates were unusually high, varying between 3.70 and 11.5 g O2 m−2 day − 1. System respiration also varied seasonally, but less than primary production. Rates were slightly higher in spring and summer.4. With one exception, P/R ratios were considerably lower than l throughout the study period, indicating that the Ogeechee River was highly heterotrophic. PIR ratios ranged from 0.09 to 1.3, and averaged 0.25.5. A carbon budget calculated for this river showed floodplain inputs were 7 times autochthonous production. Organic carbon turnover length was 690 km, considerably longer than has been reported for lower-order rivers.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 26 (1987), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In the present study we investigated the effect of lymphotoxin (LT) on the growth of human diploid fibroblasts, in the presence and absence of gamma interferon (IFN-γ). Recombinant LT (rLT) had a growth stimulatory effect on diploid human FS-4 fibroblasts. This growth-stimulatory effect was reduced in the presence of recombinant IFN-γ (rIFN-γ). LT thus has a similar effect on diploid fibroblasts as tumour necrosis factor (TNF).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 26 (1987), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Human monoeytcs release fibroblast growth-stimulatory activity. In this study tumour necrosis factor (TNF) has been identified as a major contributor to the monocyte-derived fibroblast growth-stimulaiory activity. A neutralizing monoclonal antibody (MoAb) against recombinant TNF (rTNF) inhibited growth of FS-4 fibroblasts and skin biopsy fibroblasts induced by monocyte supernatants, indicating that TNF was involved in the stimulation. Optimal growth of FS-4 fibroblasts was induced by monocyte supernatants at dilutions which cointained TNF at a concentration between 1.6 × 10−6 and 4.0 × 10−5μg/ml, less growth being induced at higher TNF concentrations. Contrary to this, no optimal concentration interval was found lor rTNF, since increasing rTNF concentrations always resulted in increased growth stimulation. It also appeared that natural TNF in the monocyte supernatants induced growth at a much lower concentration than rTNF tested in the absence of monocyte supernatant.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 890-895 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown theoretically that filamentation can lead to sizable second harmonic generation. The 2ω0 radiation is emitted into a forward-directed cone, its angle determined by the wavelength of the fundamental radiation in the plasma waveguide. Experimental observations confirm the theoretical predictions. Aside from the forward-directed emission cone, non-negligible 2ω0 power is detected over a broad angular range in the backward direction showing a broadened red-shifted spectrum.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3451-3455 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stimulated Raman scattering (SRS) in a CO2 laser(λ0=10.6 μm) produced plasma has been studied experimentally. The enhanced electron plasma wave (epw) fluctuations observed with ruby laser Thomson scattering have been compared with the scattered infrared (IR) spectra and the high-energy (near 100 keV) electrons. No scattered IR light in the range 1.5λ0 〈λ〈2λ0 was observed although the epw fluctuations suggested there should be IR light in this range. A signal was detected at 2λ0 which is due to the two plasmon decay instability. The number and energy spectra of the fast electrons are well correlated with the Thomson scattered wave vector spectra.
    Type of Medium: Electronic Resource
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